More weight loss tied to less knee pain for obese people

RALEIGH (Reuters ) – Obese people with knee osteoarthritis, a painful joint disease, may find greater symptom relief when they lose larger amounts of weight than when they shed fewer pounds, a recent study suggests.

Researchers examined data on 240 obese adults with pain from knee osteoarthritis who were participating in an 18-month experiment to see how diet alone or combined with exercise might impact their health.

Participants who lost 10 percent or more of their weight by the end of the study experienced a 50 percent reduction in pain and also reported significant improvements in mobility and daily function.

But more weight loss was even better. People who lost at least 20 percent of their weight experienced 25 percent less pain and better daily function than patients who lost no more than 10 percent of their weight, the study found.

“Our previous work has shown that when combined with mild to moderate exercise, a 5 percent weight loss over 18 months reduces pain by 25 percent and improves function and mobility compared to a control group,” said lead study author Stephen Messier of Wake Forest University in Winston-Salem, North Carolina.

“Twice that weight loss to 10 percent essentially has twice the effect,” Messier said by email. “Our new study indicates that for people who achieve a 10 percent weight loss and would like to continue losing more weight safely, they will see additional benefits in improved health-related quality of life, and reduced pain and improved function.”

Osteoarthritis is the most common joint disease in the US, affecting more than half of elderly adults. Compared with people at normal weight, obese individuals are much more likely to develop the condition and experience pain related to this joint damage.

The current study also looked at results from six-minute walking tests and found more weight loss associated with longer distances in the test. Patients had some improvement in walking distance when they lost just 5 percent of their weight, but results were much more dramatic with a 10 percent or 20 percent weight loss.

One limitation of the study is that it doesn’t show long-term effects of weight loss on knee joint pain or mobility, or show whether people are able to maintain weight loss over time or if they regain weight. It also wasn’t a controlled experiment designed to prove how the magnitude of weight loss might directly influence reductions in pain or improvements in mobility.

“Carrying extra weight puts a lot of strain on weight-bearing joints while standing, particularly the knees, because overweight and obese individuals simply have more body mass for gravity to pull toward the ground,” said Burel Goodin, a researcher at the University of Alabama at Birmingham who wasn’t involved in the study.

“The result of weight loss is less pressure on the knees, which then often means less pain in the knee joint and an easier time moving around,” Goodin said by email. “Diet and exercise are likely going to be the most helpful for losing the weight, but it is the weight loss itself that spares the knee joints.”

In addition to reducing the biomechanical strain on the knee joint, weight loss may also help curb pain from knee osteoarthritis by decreasing inflammation, said Dr. C. Kent Kwoh, director of the University of Arizona Arthritis Center in Tucson.

“The simple message is that some weight loss is good, even just 10 percent, and more weight loss is even better for all these important parameters of symptoms, function, joint load and systemic inflammation,” Kwoh, who wasn’t involved in the study, said by email.

While it’s possible to lose weight without physical activity, adding exercise to a weight loss program may help people achieve more lasting results in terms of reducing pain from knee osteoarthritis, said Anita Wluka, a researcher at Monash University in Australia who wasn’t involved in the study.

“We know that any weight loss is likely to improve symptoms over the longer term,” Wluka said by email. “Weight loss with exercise is important to maintain weight loss.”